JP2005134498A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective liquid crystal display device having high display characteristics. <P>SOLUTION: The liquid crystal display device has a liquid crystal layer 3 interposed between a front surface side transparent substrate 2 and a rear face side transparent substrate 7 and is so constituted that the rear face side transparent substrate 7 is used as a light guide plate. Thereby, a polarization layer 4 is provided between the liquid crystal layer 3 and the rear face side transparent substrate 7 and a semitransparent reflection layer 6 having a reflection region 61 and a transmission region 62 is provided between the polarization layer 4 and the rear face side transparent substrate 7. In the semitransparent reflection layer 6, the area ratio of the reflection region 61 is made lower as the reflection region is separated from a light source 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transflective liquid crystal display device.

  Conventionally, as a liquid crystal display device, a transflective liquid crystal display that displays both a reflective display using outside light such as natural light and room light and a transmissive display using illumination light from a backlight. There is a display device (see, for example, Patent Document 1). This transflective liquid crystal display device performs reflective display using outside light in a bright environment where sufficient brightness of outside light can be obtained, and in a dark environment where sufficient brightness of outside light cannot be obtained. Then, transmissive display using illumination light from a backlight is performed. For this reason, the backlight is normally turned on when transmissive display is performed.

  On the other hand, in a transmissive liquid crystal display device, a technique has been proposed in which a light guide plate is removed and a polarizing plate is inserted inside a liquid crystal display panel in order to reduce the thickness (for example, Patent Document 2).

  FIG. 6 is a schematic cross-sectional view of the liquid crystal display device proposed in Patent Document 2. In FIG. As shown in FIG. 6, the first polarizing plate 140 is attached to the outer surface, and the first substrate is arranged on the viewer side. The first substrate includes a first transparent substrate 102. A pixel electrode 104 and a switching element are formed on the inner surface of the first transparent substrate 102, and a first alignment film 106 is formed thereunder.

  A second substrate is disposed through the liquid crystal cell 130 so as to face the first substrate. The second substrate includes a second transparent substrate 112 that functions as a light guide plate. On the inner surface of the second transparent substrate 112, a second polarizing plate 150, a color filter layer 114, a common electrode 118, and a second alignment film 120 are sequentially formed. A light source 170 is disposed at one end of the second transparent substrate 112.

A plurality of reflective dots 160 are formed on the outer surface of the second transparent substrate 112. A reflector 190 is disposed below the second transparent substrate 112.
JP 2000-187220 A Japanese Patent Laid-Open No. 2003-121824

  In the liquid crystal display device having the structure shown in FIG. 6, light incident from the light source 170 is converted into a surface light source by a plurality of reflective dots 160 formed on the outer surface of the second transparent substrate 112. At this time, the reflective dots 160 are generally increased in density as they move away from the vicinity of the light source 170 to control the directivity of light from the light source 170. This makes it possible to make the amount of light uniform over the entire screen. In the structure shown in FIG. 6, the light incident from the light source 170 is not totally reflected at the front-side interface of the second transparent substrate 112, that is, the interface with the second polarizing plate 150, and has a specific vibration direction. It will be absorbed by the second polarizing plate 150. For this reason, the light incident from the light source 170 does not travel efficiently in the second transparent substrate 112, and it becomes difficult to emit uniform light to the front side as the entire screen.

  The object of the present invention is to adopt a new method for uniforming the amount of light from the light source over the entire screen when the rear transparent substrate functions as a light guide plate in a transflective liquid crystal display device. An object of the present invention is to provide a liquid crystal display device.

  The liquid crystal display device according to the present invention includes a first transparent substrate, a second transparent substrate that is provided to face the first transparent substrate and functions as a light guide plate, the first transparent substrate, and the first transparent substrate. A liquid crystal layer provided between two transparent substrates, a polarizing layer provided between the liquid crystal layer and the second transparent substrate, and provided between the polarizing layer and the second transparent substrate, A semi-transparent semi-reflective layer having a reflective region and a transmissive region is provided, and in the semi-transmissive semi-reflective layer, the area ratio of the reflective region is lowered as the distance from the light source is increased. With such a configuration, light from the light source can be emitted uniformly from the front surface over the entire screen, and display characteristics can be improved.

  Further, an absorptance control layer is provided between the polarizing layer and the transflective layer, and in this absorptivity control layer, the absorptance of light in a region where the area ratio of the reflective region in the transflective layer is high. Is preferably higher than the light absorptance of the region where the area ratio of the reflective region is low. With such a configuration, it is possible to make the light reflected from the external light and emitted to the viewer side uniform over the entire screen, and the display characteristics can be improved.

  Furthermore, the absorptance control layer may have a diffusing material. In particular, the directivity of light from the light source can be controlled by the diffusing material.

  Moreover, the absorptance control layer in a preferred embodiment has a printed layer formed on the reflective region of the transflective layer.

  You may make it perform a scattering process on the back side surface of a said 2nd transparent substrate. For example, the scattering process is performed by printing reflective dots or forming prisms.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which employ | adopted the new system which equalizes the light quantity from a light source over the whole screen can be provided.

Embodiment 1 of the Invention
FIG. 1 shows a configuration of a liquid crystal display device according to Embodiment 1 of the present invention. This liquid crystal display device is a so-called transflective liquid crystal display device. As shown in the figure, in the liquid crystal display device, from the front side, the polarizing layer 1, the front side transparent substrate 2, the liquid crystal layer 3, the polarizing layer 4, the absorptance control layer 5, the transflective layer 6, the rear side transparent. A substrate 7 and a reflective layer 8 are arranged in this order.

  The polarizing layer 1 is composed of, for example, a polarizing film, transmits a linearly polarized light whose transmission axis and absorption axis are orthogonal to each other, parallel to the transmission axis, and absorbs linearly polarized light parallel to the absorption axis. A retardation layer may be further provided between the polarizing layer 1 and the front transparent substrate 2. This retardation layer is composed of a retardation plate, a retardation film, and a laminate thereof, and converts linearly polarized light into elliptically polarized light.

  The front-side transparent substrate 2 is a transparent substrate disposed on the viewer side, and is made of, for example, glass or transparent resin, on which a transparent electrode such as ITO is formed. The liquid crystal layer 3 is a layer made of, for example, nematic liquid crystal provided between the front transparent substrate 2 and the rear transparent substrate 7.

  The polarizing layer 4 is formed on the absorptance control layer 5 by a coating process, and allows only linearly polarized light having a vibration direction parallel to a specific transmission axis to pass therethrough. The polarizing layer 4 has a thickness of 500 nm, for example. In the embodiment of the present invention, the polarizing layer 4 is thus provided between the liquid crystal layer 3 and the back side transparent substrate 7.

  The polarizing layer 4 aligns the dye on the transparent substrate 7 on the rear side subjected to the alignment treatment, or aligns the dye by irradiating light after applying the dye, and further follows the application direction at the time of applying the dye. The absorption axis is defined by orienting the dye. For example, a method disclosed in US Pat. No. 6,174,394 can be used as a method for applying the polarizing layer 4. A transparent electrode such as ITO is formed on the upper surface of the polarizing layer 4.

  A color filter (CF) layer may be formed between the polarizing layer 4 and the absorptance control layer 5. The CF layer has R (red), G (green), and B (blue) regions, and realizes color display by controlling the amount of light that passes through these regions. The CF layer 6 has a thickness of 2 μm, for example.

  The absorptance control layer 5 is provided on the transflective layer 6. In the present invention, the absorptance control layer 5 is configured such that the area ratio between the reflective region 61 and the transmissive region 62 in the semi-transmissive / semi-reflective layer 6 is a distance from the light source 9 so that light from the light source 9 is uniformly emitted on the screen. Along with the change, the absorption rate is controlled in order to make the reflected light from the reflection region 61 of the transflective layer 6 uniform on the screen. More specifically, control is performed so that the absorptance increases in a region where the area ratio of the reflective region 61 is high, and the absorptance is controlled in a region where the area ratio of the reflective region 61 is low.

  The transflective layer 6 has a reflective area 61 and a transmissive area 62. The reflective region 61 is formed of a reflective layer, and is provided in the same layer as the transmissive layer that forms the transmissive region 62. The reflection region 61 reflects light incident from the front side to the front side. The transmission region 62 transmits the light incident from the front side and emits it to the back side, and also transmits the light incident from the back side and emits it to the front side.

  In this example, the reflective region 61 is patterned to form the transmissive region 62 intermittently, and the reflectance and transmittance are controlled. As described above, the area ratio between the reflective region 61 and the transmissive region 62 is changed according to the distance from the light source 9 so that the light from the light source 9 is emitted uniformly over the entire screen. Specifically, in the region where the distance from the light source 9 is short, the total reflection condition is not satisfied at the interface between the semi-transmissive and semi-reflective layer 6 and the back side transparent substrate 7 as compared with the region where the distance from the light source 9 is far. Since the amount of light emitted to the front side is larger, the area ratio of the transmission region 62 is reduced so as to be uniform over the entire screen. On the contrary, in a region far from the light source 9, the amount of light emitted from the interface between the transflective layer 6 and the back side transparent substrate 7 is low, so the area ratio of the transmissive region 62 is increased.

  The transflective layer 6 is formed by metal sputtering or the like. At this time, the reflectance and transmittance can be controlled by controlling the film thickness. In general, from the viewpoint of ease of control of reflectance and transmittance, it is preferable to form an opening in a metal sputtered film by etching or the like.

  The back side transparent substrate 7 is, for example, a glass substrate, or a transparent resin substrate such as polycarbonate or acrylic resin. No retardation layer is provided on the back side of the back side transparent substrate 7. In the first embodiment of the present invention, the back side transparent substrate 7 is not subjected to processing for directivity control processing such as reflective dots. A light source 9 is provided in the vicinity of the side surface of the back side transparent substrate 7, and light incident on the side surface from the light source 9 is emitted as planar light from the front side. Therefore, the back side transparent substrate 7 forms an electrode and functions as a light guide plate that converts light from the light source 9 into planar light in addition to the function of holding the liquid crystal layer between the back side transparent substrate 2 and the front side transparent substrate 2. It has a function.

  The reflective layer 8 is provided on the back side of the back side transparent substrate 7 through an air layer. The reflective layer 8 has a function of reflecting light leaked from the back side transparent substrate 7 to the back side transparent substrate 7 side.

  The light source 9 is disposed in the vicinity of the side surface of the back side transparent substrate 7. A point light source may be used instead of a linear light source. For example, as the light source 9, a cold cathode ray tube, a light emitting diode (LED), electroluminescence, a small incandescent bulb, an organic EL, or the like is used.

  In FIG. 2, the structural example of the absorptance control layer 5, the semi-transmissive semi-reflective layer 6, and the back side transparent substrate 7 is shown. On the upper surface of the back-side transparent substrate 7, a reflective layer that forms the reflective region 61 of the transflective layer 6 is formed. The portion where the reflective layer is not formed becomes the transmissive region 62. A print layer 51 is provided on the upper surface of the reflection region 61 in order to control the absorption rate. An overcoat layer 52 made of a transparent resin or the like is formed so as to cover the print layer 51. The overcoat layer 52 includes a granular diffusion material 53 having a refractive index different from that of the transparent resin forming the overcoat layer. The absorptance control layer 5 is constituted by the print layer 51, the overcoat layer 52, and the diffusion material 53.

  The print layer 51 is made of the same material as that of the black matrix layer. For example, resin black in which carbon or titanium is dispersed in a photoresist, metal chromium, or nickel can be used. The print layer 51 is formed so as to have a larger area in a region where the absorption rate needs to be increased, and is formed so as to have a smaller area in a region where the absorption rate needs to be reduced. In the example shown in FIG. 2, the individual dots forming the printing layer 51 have the same size, but by changing the density, the area of the printing layer 51 is controlled and the absorption rate is controlled accordingly. Yes.

  The diffusion material 53 of the absorptance control layer 5 has a function of diffusing light incident from the back side transparent substrate 7 side and diffusing light reflected by the reflection region 61. With this diffusing material 53, the directivity can be controlled by diffusing light traveling from the back side transparent substrate 7 side to the front side through the transmissive region 62 of the transflective layer 6.

  FIG. 3 shows a top view in a state in which the reflective layer and the print layer 51 are formed on the upper surface of the back-side transparent substrate 7. In FIG. 3, a light source is provided on the left side of the drawing. In the example shown in the figure, the reflective layer constituting the reflective region 61 is formed in a lattice shape, and the region where the reflective layer is not formed becomes the transmissive region 62. The print layer 51 is formed so that the number of dots forming the print layer 51 is increased in a region where the area ratio of the reflection region 61 in the left part of the drawing is large, and the area ratio of the reflection region 61 in the right part is It is formed so as to decrease in a small region. In this way, the reflected light from the reflection region 61 can be made uniform over the entire screen.

  In the first embodiment of the present invention, as described above, the directivity control process using the reflective dots or the like is not performed on the back side of the back side transparent substrate 7. An air layer is present on the back side of the back side transparent substrate 7. Therefore, the light incident from the light source 9 proceeds while being totally reflected at the front-side interface and the back-side interface of the back-side transparent substrate 7, and light that does not satisfy the total reflection condition is emitted from the front side. After being reflected by the reflective layer 8, it is emitted from the front side. At this time, the transflective layer 6 located on the front surface side of the rear transparent substrate 7 has an area of the reflective region 61 and the transmissive region 62 so that the light from the light source 9 has a uniform light quantity over the entire surface. Since the ratio is controlled, a uniform amount of light can be emitted over the entire surface. Further, the outside light reflected by the reflection region 61 can be made uniform over the entire screen by the absorptance control layer 5. In this way, the display characteristics of the liquid crystal display device can be improved.

Embodiment 2 of the Invention
In Embodiment 1 of the invention, the directivity control processing is not performed on the back side transparent substrate functioning as the light guide plate, and no processing is performed on the back side surface of the back side transparent substrate. In the liquid crystal display device according to the second embodiment of the invention, the reflective dots are formed on the back surface of the back transparent substrate. FIG. 4 is a schematic cross-sectional view of the liquid crystal display device. In FIG. 4, only the configuration of the back-side transparent substrate 7 is different from the liquid crystal display device according to the first embodiment of the invention, and the other configurations are the same, so the description is omitted.

  As shown in the figure, reflective dots 71 are formed on the back side surface of the back side transparent substrate 7. The reflective dots 71 are arranged substantially uniformly on the back side surface of the back side transparent substrate 7. Therefore, the reflective dot 71 controls the directivity, but does not change the directivity control according to the distance from the light source 9. Accordingly, the amount of light emitted from the front surface of the back-side transparent substrate 7 having such a configuration increases on the side closer to the light source 9 and decreases as the distance from the light source 9 increases.

  For this reason, also in the second embodiment of the present invention, the area ratio of the reflective region 61 and the transmissive region 62 of the semi-transmissive / semi-reflective layer 6 is controlled as in the first embodiment of the present invention. Specifically, the area ratio of the reflection region 61 on the side close to the light source 9 is increased, and the area ratio of the reflection region 61 is decreased as the distance from the light source 9 increases.

  As the directivity control processing in the back side transparent substrate 7, in addition to forming the reflective dots 71, a prism may be formed on the back side surface of the back side transparent substrate 7, or scattering processing may be performed. Good.

  Also in the second embodiment of the present invention, similarly to the first embodiment of the present invention, a uniform amount of light can be emitted over the entire surface, thereby improving the display characteristics of the liquid crystal display device. .

Embodiment 3 of the Invention
In Embodiment 1 of the invention, the directivity control processing is not performed on the back side transparent substrate functioning as the light guide plate, and no processing is performed on the back side surface of the back side transparent substrate. In the liquid crystal display device according to the third embodiment of the present invention, reflective dots are formed on the back surface of the back transparent substrate. FIG. 5 shows a schematic cross-sectional view of the liquid crystal display device. In FIG. 5, only the configuration of the back-side transparent substrate 7 is different from the liquid crystal display device according to the first embodiment of the invention.

  As shown in the figure, reflective dots 71 are formed on the back side surface of the back side transparent substrate 7. The reflective dots 71 in the second embodiment of the invention are arranged substantially uniformly on the rear surface of the rear transparent substrate 7, but the reflective dots 71 in the third embodiment of the present invention are The directivity control is changed according to the distance. Specifically, the reflective dots 71 are formed such that the density thereof increases as the distance from the light source 9 increases. That is, the distance from the light source 9 increases as the distance from the light source 9 increases.

  In Embodiment 3 of the present invention, although the directivity control is changed by the reflective dots 71 and the like as described above, the light amount of the entire screen is not uniformed, and the semi-transmissive / semi-reflective layer By controlling the area ratio of the reflective region 61 and the transmissive region 62 in FIG.

  In other words, in Embodiment 3 of the present invention, both the change in directivity control in the back side transparent substrate 7 and the change in the area ratio of the reflective region 61 and the transmissive region 62 in the semi-transmissive / semi-reflective layer 6 are performed simultaneously. As a result, the light quantity of the entire screen is finally made uniform.

  Specifically, also in Embodiment 3 of the present invention, the area ratio of the reflection region 61 on the side close to the light source 9 is increased, and the area ratio of the reflection region 61 is decreased as the distance from the light source 9 increases.

  As the directivity control processing in the back side transparent substrate 7, in addition to forming the reflective dots 71, a prism may be formed on the back side surface of the back side transparent substrate 7, or scattering processing may be performed. Good.

  Also in the third embodiment of the present invention, similarly to the first embodiment of the present invention, a uniform amount of light can be emitted over the entire surface, thereby improving the display characteristics of the liquid crystal display device. .

It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the liquid crystal display device concerning this invention. It is a fragmentary sectional view of the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizing layer 2 Front side transparent substrate 3 Liquid crystal layer 4 Polarizing layer 5 Absorptivity control layer 6 Transflective semi-reflective layer 7 Back side transparent substrate 8 Reflecting layer 9 Light source 51 Printing layer 52 Overcoat layer 53 Diffusing material 61 Reflecting region 62 Transmitting Area 71 Reflective dots

Claims (5)

A first transparent substrate;
A second transparent substrate that is provided opposite to the first transparent substrate and functions as a light guide plate;
A liquid crystal layer provided between the first transparent substrate and the second transparent substrate;
A polarizing layer provided between the liquid crystal layer and the second transparent substrate;
A transflective layer provided between the polarizing layer and the second transparent substrate and having a reflective region and a transmissive region;
In the transflective layer, the area ratio of the reflective region is decreased as the distance from the light source is increased. An absorptivity control layer is provided between the polarizing layer and the transflective layer,
The said absorptance control layer WHEREIN: The light absorptivity of the area | region where the area ratio of the reflective area | region in the said semi-transmissive semi-reflective layer is high becomes higher than the light absorptivity of the area | region where the area ratio of a reflective area | region is low. 1. A liquid crystal display device according to 1.   The liquid crystal display device according to claim 2, wherein the absorptance control layer includes a diffusing material.   4. The liquid crystal display device according to claim 2, wherein the absorptance control layer has a printed layer formed on a reflective region of the transflective layer. The liquid crystal display device according to claim 1, wherein a scattering treatment is performed on a back surface of the second transparent substrate.

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